Radio telegraph system



7, 1935. 1.. R. SCHMITT 2,012,407

RADIO TELEGRAPH SYSTEM Filed June 13, 1932 FIG. 1

INVENTOR AAWPf/VCf E. SCHM/TT ATTORN line winding 44 of the polar relay 39 and through a winding 45 of the milliammeter 4| to the battery 42. Filament rheostats 45 and 41 regulate the temperature of cathodes 48 and 49 respectively, the filaments being heated by current from an A-battery 54. The windings 38 and 44 of polar relay 38 operate the armature 5|] which closes at all times one or the other of two con tacts 5| and 52. Should a printer 55 be neutral to polarity, its armature having a return spring, then the spacing contact 52 may be left unconnected as shown and the marking contact 5| may be provided with a battery of either polarity. Should the printer 55 be of polar nature, batteries of two polarities are provided upon the contacts 5! and 52.

Current from battery 42 through the biasing winding 38 of the polarized relay 39 is capable of adjustment by means of resistance |2 which is included in. circuit with an inductance l3. The inductance l3 functions as a choke coil to prevent the introduction of extraneous currents in the output circuit of the vacuum tube 32. Through adjustment of resistance l2, the value of the biasing current on winding 38 may be varied to suit particular conditions.

In adjusting the relay system I8 for operation in response to signals received from the transmitter disclosed in Fig. 1, test keys 5'1 and 58 are opened, and that circuit path of the relay system which includes the transformer secondary winding 22, condenser 24, vacuum tube 32, and winding 38 is tuned, by adjusting the condenser 24, to produce a maximum or desired deflection in the milliammeter 4|. The purpose of first tuning and then detuning the circuit is to place it in a condition very near the resonance with the frequency of the predetermined single audio-frequency current, but substantially completely out of resonance with such frequency, so that little or no current of the frequency of the signal will flow in the circuit. Key 58 is then closed and the other circuit path of the relaysystem, which includes the transformer secondary winding 23, condenser 25, vacuum tube 33. key 58, and the winding 44, is tuned by adjusting the condenser 25, to its point of resonance with the predetermined single audio-frequency signal or to pro duce a maximum or desired deflection of the milliammeter 4!. Of course, the above described conditions are established subsequent to the adjustment of the biasing effect resulting from the C battery 36, as is well understood in the operation of circuits of the character disclosed in the drawing. After noting the deflection of the milliammeter 4| in response to the adjustment of condenser 25, key 5'! is closed and rheostat I2 is adjusted to reduce the deflection of the milliammeter 4! to one-half of the value previously indicated thereon through the adjustment of condenser 25. The current flowing through winding 38 of polarized relay 39 is now suflicient to maintain armature in contact with contact 5! when signals are not being impressed on the antenna H in response to the operation of the transmitter disclosed in Fig. 1. However, when signals are received on the primary winding 2! of the transformer 2'3, Fig. 2, vacuum tube 33, having its input circuit tuned to such frequency, respends accordingly, and current flows in its output circuit, energizing winding 44 of the polarized relay 39. The effect of current through winding is sufficient to counteract or overcome the action of current through winding 38 of the polarized relay 39 and thus move its armature 58 from engagement with contact 5| into engagement with contact 52, causing the corresponding operation of the printer 55.

The operation of the system is as follows:

A continuous signal radiated from the antenna is received by the antenna H and results in a continuous current through the winding 44 of the relay 39 which controls the armature 50 in the position shown. The current through the winding 44 is opposed by a current of half the volume and in the opposite direction through the winding 38 which is produced in the winding 38 by the rheostat l2 and the battery 42. There is no current through the tube 32 during the period of normal signaling. Upon cessation of the signal by opening the contacts I to permit the relay 9 to shunt the winding 3, the current through winding 44 ceases and the current through winding 38 controls the armature to move to its opposite position. To this change in position of armature 50 the printer 55 responds. Alternating periods of current and no-current upon the antenna I l and in the winding 44 result in the proper operation of the printer 55 to record the received message.

The system including winding 22, condenser 24 and electronic valve 32 does not furnish any current at any time in normal operation because it is tuned out of the frequency which operates electronic tube 33 but is tuned so near to that frequency that it is out of any other frequency in use by any other system at that time.

Should a static disturbance produce effects on the antenna II and therefore in the primary winding 2| the effects will be transferred to both of the windings 22 and 23 and will effect both of the electronic valves 32 and 33 to produce slmultaneous but opposite magnetic efiects in the polar relay 39 thus producing no effect upon the armature of that relay and producing no effect in the printer 55. This is the neutralizing condition for which the elements 22 and 32 are present in the structure.

Although the invention has been described in connection with a specific form thereof it will be understood that it has further applications and it is not intended to be limited in scope by the embodiment shown herein for illustration.

The invention claimed is:

1. In a receiving system for single-frequency radiant-energy telegraph systems, an antenna, an audio-frequency transformer, a first local circuit associated with said antenna through said audio-frequency transformer and tuned to the audio-frequency of the heterodyned signal and subject to both signal currents and static disturbance upon said antenna, a first key to open said first circuit, a second local circuit similarly associated with said antenna and detuned from the said audio-frequency and subject to static disturbance only upon said antenna, a biased polar relay, an operating winding and a biasing winding for said relay, said relay having said first circuit connected with its operating winding and said second circuit connected with its biasing winding, a biasing circuit connected as a derived circuit upon said second circuit, a second key to open said biasing circuit, and a printing telegraph recorder controlled by the contacts of said polar relay.

2. In a receiving circuit for single frequency radio telegraph signals, a detector circuit having two paths, one tuned to a predetermined single audio-frequency or" a heterodyned signal and subject also to currents generated by static disturbances, and the other path detuned to said predetermined single audio-frequency to determine determined single audio-frequency but subject to the degree of bias on said biasing winding, circuit currents generated by static disturbances, a pointerrupting means local to the detector and inlarized relay connected to said two paths having cluded in the respective paths for rendering said 6 an operating and a biasing winding, with the oprespective paths efiective or non-effective on the 6 crating winding responsive to currents of the prewindings of said polarized relay, and a recorder determined single audio-frequency current and controlled by said polarized relay in its response the biasing winding non-responsive thereto, to current through the path tuned to said audiomeans connected in circuit with said biasing frequency current.

10 winding and the path which is detuned to the pre- LAWRENCE R. SCHMI'I'I. 10 

